\begin{tikzpicture}
    \pgfmathsetmacro{\a}{2.5}
    \tkzDefPoints{0/0/B,  \a/0/C}
    \tkzDefPoint(60:\a){A}
    \tkzDefShiftPoint[C](60:\a){D}
    \tkzDrawPolygon(A,B,C,D)
    \tkzLabelPoints[left](A,B)
    \tkzLabelPoints[right](C,D)
\end{tikzpicture}

